“Adipose tissue” or (body) “fat” is loose connective tissue composed mostly of adipocytes or “fat cells”. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular endothelial cells and a variety of immune cells (cf. https://en.wikipedia.org/wiki/Adipose_tissue). Far from being inert, it has been established that adipose tissue can produce hormones, and is an abundant source of CD34+ cells (cf. Traktuev et al., Circ Res. 2008 Jan. 4; 102(1): 77-85. Epub 2007 Oct. 25, also available in http://www.ncbi.nlm.nih.gov/pubmed/17967785). CD34+ cells are a mixture of stem cells, progenitors, and white blood cells of various degrees of maturity.
Excess adipose tissue can be removed from a specific location of a body by liposuction. In liposuction, a hollow cannula comprising an opening at or close to its free end, is inserted into the region of the body to be treated through a small incision in the skin. Fat cells are aspirated through the lumen of the cannula which is connected to a vacuum source and thus driven into a container. Liposuction can be applied for therapeutic reasons to treat obesity, which is an excess of adipose tissue, or it can be applied for cosmetic reasons to improve one's figure.
As improving one's figure is not restricted to removing adipose cells from locations where it is considered they are present in excess, but may also comprise giving volume to locations of the body considered as volume deficient, it has rapidly been proposed to re-inject a fraction of the adipose tissue extracted from one location of the body in excess of body fat, into another location deficient in adipose tissue, like e.g., lips, cheeks, breast. This solution is appealing since there is no risk of rejection of its own cells by the patient. The extraction of adipose tissue is often referred to as “liposuction”, the re-injection as “lipofilling” and, in cosmetic applications, a liposuction followed by a lipofilling is often artistically referred to as “liposculpture.” Unfortunately, it has been observed that, when the “sculptural” result obtained at the end of a lipofilling operation could be fully satisfactory, with an increase in volume of those parts of the body which were considered as in need, said result rapidly decayed with time with a substantial loss of volume of the order of 50 to 60% after a few days only. Lipofilling effects were declared to be transient only. Two solutions were proposed. First, it was proposed to increase the lipofilling volume during the operation such that, the time dependent loss of volume would eventually yield the desired volume. It is clear that such solution has two major inconveniences: the “sculptural” effect after the operation is certainly not at the level of expectation of the patient, and it is difficult to establish with certainty the percentage of volume loss with time. The second solution which was proposed, and is still widely in use today, is to store the extracted adipose tissue and to re-inject it in small doses in several lipofilling interventions spread in time, like the repetitive brush strokes given by a painter to give depth to its composition. But if the art comparison in the term “liposculpture” is appealing, it is clear that for the patient it is very inconvenient to undergo a series of lipofilling interventions, which are rather intrusive, long (ca 0.5-1.5 h), carried out under anaesthesia (at least local), and which can form an hematoma at the re-injection point(s) for several days each time. Furthermore; the risks of degradation or infection of the adipose cells increase with storing time.
It is believed with sufficient certainty, that the reason for the transient effect of lipofilling is due to the fact that adipose tissue is extracted by liposuction in the form of lumps or agglomerates of adipocytes and other cells, as illustrated in FIG. 3(a), left hand side. As adipose tissue is re-injected in the body, vascularization of the cells begins. If the adipose cells present at the periphery of the agglomerate are easily vascularized, this is not the case of the cells present in the core of the agglomerate. The core cells rapidly die due to necrosis and the thus hollow agglomerate collapses and flattens, thus explaining the loss of volume observed with time after a lipofilling operation (cf. FIG. 3(a), right hand side, shaded cells indicate necrosis).
Re-injection of a fraction of the adipose tissue extracted by liposuction is drawing more and more attention in therapeutical applications, in particular for the recovery and re-injection of regenerative cells abundantly present in adipose tissue, such as for examples stem cells, in particular CD34+ cells, sometimes referred to as adipose derived stem cells (ADSC). If adipose cells necrosis is inconvenient in liposculpture for cosmetic applications, it is a major drawback for the collection and re-injection of specific cells like stem cells.
A liposuction device comprises a long, hollow cannula coupled to a handpiece, with one or more openings at or adjacent to the tip end thereof. The lumen is in fluid communication with an extracting tube and with a vacuum pump for driving the extraction of the adipose tissue, when the tip end of the cannula is inserted within the adipose tissue to be treated. Liposuction devices may or may not have a power assisted handpiece, suitable for imparting a given movement, generally a reciprocal movement, to the tip of the cannula.
U.S. Pat. No. 4,536,180 mentions a manual (i.e., non-powered) liposuction device, wherein no additional movement is imparted to the cannula by a power source. U.S. Pat. No. 6,494,876 mentions a liposuction device wherein a cannula is attached to a power assisted handpiece which reciprocates the cannula back and forth along the longitudinal axis of the cannula at a frequency of 400 to 800 cycles per min (=6.7-13.3 Hz). Similarly, U.S. Pat. No. 5,911,700 mentions a powered liposuction device reciprocating back and forth the cannula along its longitudinal axis at an amplitude of 1 to 10 mm. International Patent Publication WO9844966 mentions a powered liposuction device imparting to the cannula a combined movement of longitudinal back and forth reciprocation at a frequency of 10 to 500 Hz and a movement of nutation (vibrating and orbiting movements combination of the tip end of the cannula about the longitudinal axis thereof at rest). None of the foregoing disclosures addresses survival of the extracted adipose tissue thus extracted. Of course, there are many more disclosures of liposuction devices, but few address survival of the extracted adipose tissue because extracted adipose tissue is generally simply destroyed or disposed of after extraction.
International Patent Publication WO2011146924 describes a power assisted liposuction device for extracting adipose cells generating ultrasonic energy transmitted to the cannula. The ultrasonic frequency, f, is restricted between 35 and 45 kHz because, according to the authors, all ultrasonic frequencies are not appropriate for cell survival, as it seems to be the case for Lysonix® liposuction device discussed therein. WO2011146924 teaches that the adipose tissue thus extracted can be filtered to remove the larger material and the filtrate contains the adipose derived stem cells (ADSC's). The removal of larger material strongly suggests that agglomerates of adipocyte cells are extracted by liposuction and discarded by the filtration operation, resulting in a great loss of potential ADSC's present in the discarded adipocyte agglomerates.
U.S. Pat. No. 5,911,700 describes a power assisted liposuction device for extracting adipose cells using a powered liposuction device. In one embodiment, a filtering means is interposed between the liposuction device and a vacuum pump to separate a selected portion of adipose tissue from undesired material. The pump can then be reversed to pressurize the selected portion of adipose tissue and drive it back towards the liposuction device used this time as lipofilling device. It is clear that such description has never been implemented because it does not make sense to use a powered handpiece to inject tissues into a part of a body requiring extreme precision, the movement of the cannula preventing any targeted injection of tissues. Furthermore, the cannulas used in lipofilling are different from the ones used for liposuction, the former being generally thinner and, in particular, comprising a single outlet at the tip of the cannula, whilst liposuction devices generally comprise a multitude of inlet windows at the tip of the cannula. Injecting tissues with a cannula comprising several outlets does not permit any precise injection work.